1. Field of the Invention
The present invention is directed generally to a blood pressure measuring system, and more particularly to an improved blood pressure measuring system utilizing oscillometric methods for determination of the blood pressure measurements of a test subject.
2. Description of the Prior Art
There have been proposed in the art a number of blood pressure measuring systems based upon the oscillometric methods, for example, as shown in U.S. Pat. Nos. 4,263,918 and 4,407,297. The prior systems relying upon the oscillometric methods handle the fluctuating quantity representative of each blood pressure pulse appearing within an artery of the subject under a changing external pressure of occluding the artery for the purpose of analyzing the oscillometric pulse train and determining systolic and diastolic pressures. The practical implementation of the system is to employ a pressure transducer which delivers at a suitable sampling rate the cuff pressure data including the occluding pressure plus the blood pressure pulse superimposed thereon. In the above prior system, the blood pressure pulse is extracted from the cuff pressure data in the form of a pulse height or peak value as representing the fluctuating or pulsating quantity.
But unfortunately, the blood pressure pulse superimposed on the occluding pressures is known to be normally as small as 5 mmHg in height, which not only makes the extraction technique thereof difficult but also makes the extracted value rather incompetent against possible artifacts which frequently accompany an even slight movement of the subject during the measurement cycle or unavoidable artifacts generated within the body of the subject. Accordingly, the prior systems recognizing the blood pressure pulses by their pulse height are susceptible to the artifacts and likely to result in false or erroneous calibration, which should be eliminated for effectuating accurate and easy blood pressure measurements.